MCi Crusader II 1989 Maintenance Manual page 493

Date
1-1-89
Page __
16_-2_3 _ _
MC-9 MAINTENANCE MANUAL
Discharge gas bleeds from behind the bypass piston to the
suction manifold. The bypass piston opens, discharge gas
is recirculated back to the suction manifold and the
cylinder bank is unloaded. Reduction in discharge pres-
sure causes the check valve to close. isolating the cylinder
·bank from the discharge manifold.
COMPRESSOR LUBRICATION SYSTEM
Force-,feed lubrication of the compressor is accomp-
lished by a low-speed oil pump.driven directly from the
compressor crankshaft. Refrigeration oil is drawn from the
compressor crankcase through the oil filter screen and
pick-up tube to the oil pump located in the bearing head
assembly. The crankshaft is drilled to enable the pump to
supply oil to the main bearings, connecting rod bearings,
and the shaft seal. The lubricating oil is pumped, under
pressure, through the lube system by a lobed-rotor type oil
pump.
The oil flows to the pump end main bearings, connecting
rod bearings and seal end main bearings, where the oil path
is divided into two directions. The largest quantity flows to
the oil relief valve, which regulates oil pressure at 15 to 18
psi (103.5-120.5 kPa) above suction pressure. When the oil
pressure reaches 15 to 18 psi (103.5-120.5 kPa) above suc-
tion pressure, the relief valve spring is moved forward
allowing oil to return to the crankcase. The remaining oil
' 1 ows through an orifice and into the shaft seal cavity to
.,rovide shaft seal lubrication and cooling. This oil is then-
returned to the crankcase through an overflow passage
(figure 16-23).
EQUALIZATION HOLE
Figure 16-23: Compressor Lubrication Diagram
An additional oil pressure relief valve, built into the oil
pump, is open at speeds above 400 rpm to relieve a portion
of the oil pressure to the crankcase in order to maintain oil
riressure below an acceptable maximum. At low speeds,
e valve is closed to ensure adequate oil pressure at 400
rpm. At speeds above 1,900 rpm, the oil pressure will be 25
to 30 psi (172.5-207 kPa) above suction pressure.
The oil pressure equalization system consists of two oil
return check valves and a ¼-inch pressure equalization port
between the suction manifold and crankcase. Under nor-
mal conditions, check valves are open and allow for oil
return to the crankcase. Under flooded start conditions.
pressure rises in the crankcase and closes the check valves,
preventing excess oil loss. The equalization port allows for
release of excessive pressure. that has built up in the
crankcase, to the suction manifo!d; this ensures that the oil
loss is kept to a minimum.
SUCTION AND DISCHARGE SERVICE VALVES
The suction and discharge service valves on the com-.
pressor are equipped with mating flanges for connecting to
flanges on the compressor. These valves are provided with
a double seat and a gauge connection, which enables ser-
vicing of the compressor and refrigerant lines (figure
16-24).
TO SUCTION OR
DISCHARGE LINE
GAUGE CONNECTION (PLUG)
J
VALVE CAP
VALVE
STEM
TO COMPRESSOR
Figure 16-24: Suction/Discharge Valve
Turning the valve stem clockwise (all the way forward)
frontseats the valve, closing off the suction arid discharge
lines and opening up the gauge connection to the com-
pressor. Turning the valve stem counterclockwise (all the
way out) backseats the valve, opening the suction or dis-
charge line to the compressor and closing off the gauge
connection.
With the valve stem• midway between frontseated and
backseated positions. suction or discharge line is open to
both the compressor and the gauge connection.
For example, when connecting manifold gauge to mea-
sure suction or discharge pressure. ensure valve stem is
fully backseated. Then, to measure suction or discharge
pressure partially frontseat (about two turns) the valve
stem.
SETTING UNLOADERS (Engine Side) - Before setting
unloaders, fully backseat the suction service valve and
install the low pressure service gauge into the suction ser-
vice valve.
1. Remove the cap from the differential adjustment screw
and turn the screw out until it is approximately 2 turns from
backstop.
2. Turn the unloader adjusting nut as far back as possi-
ble, without removing it.
3. With the engine running and A/Con, partially frontseat
the suction service valve until the pressure gauge reads 30
psi (207 kPa).